1. Field of the Invention
This invention relates to a paint film structure formed on the surface of an aluminum member aluminum alloy member such as, for example, an aluminum wheel of automotive vehicles.
2. Brief Description of the Prior Art
Heretofore, an organic substance system paint film has been used as a paint film formed on an aluminum member or aluminum alloy member such as, for example, an aluminum wheel, because the paint film can be made thick and the burning temperature of the coating material is not very high.
However, it has the following disadvantages.
(1) Since the organic substance system paint film has a weak affinity with respect to the surface of a metal, the aluminum member or aluminum alloy member is apt to corrode.
(2) Since the organic substance system paint film has a strong affinity with respect to a stain, it is difficult to clean the stain attached to the surface of the paint film. In addition, since this paint film is readily damaged, the fancy appearance of the aluminum member or aluminum alloy member is spoiled.
On the other hand, an attempt has been made for applying an inorganic substance system paint film on the surface of the aluminum member or aluminum alloy member. However, it also has the following disadvantages.
(1) If the inorganic substance system paint film is made thick, it is easily separated from or swollen out of the surface of the aluminum member of aluminum alloy member.
(2) Since the burning temperature of the coating material is high, the aluminum member or aluminum alloy member is easily changed in quality when burning.